In prior art, flat magnets are used in a wide variety of applications as floor and bench mats for workshops to catch highly magnetic dropped screws and nuts etc; for hanging tools on a wall; for attaching signs to a flat magnetic surface; for therapeutic purposes; as magnetic chute bottoms, as plate or suspension magnets at discharge of conveyors, suspended above conveyed materials and under or at the discharge of vibrating conveyors or feeders. Flat plate and suspension magnets are frequently positioned above moving material and have as simple magnet circuit with a comparatively wide space (air gap) between unlike poles for cost reduction reasons and to obtain depth of magnetic field. Consequently, a great proportion of the available magnetic energy from the magnet components is used to draw magnetic contamination through the material depth, in some situations also through a clearance gap and onto the magnet surface.
In the prior art, “depth of pull” is a prime consideration, and to achieve this, magnets are often extremely heavy and have deep fields at the expense of shallow fields of high flux density.
One or more retention steps, or a recessed air gap machined in the plate magnet surface is sometimes employed to improve retention of fine particles or spherical iron pieces. These are however, necessarily wide apart, few in number, form part of the magnet surface and (not being detachable) are more difficult to clean.
Non-magnetic covers or cover plates are sometimes employed on the working face of magnetic devices or flat face magnets and suspension magnets of prior art for the sole purpose of making such magnets easier to clean. Such covers do not increase the retention ability of the magnet. Because such quick cleaning covers increase the distance from an already weak magnetic working face, the ability of the magnet to retain weakly magnetic fines and fragments against opposing forces is thereby even further reduced.
Some prior art magnets used in industry have a strong magnetic influence, and in some instances there is a disadvantage with occupational health and safety issues with the manufacture and assembly of magnetic apparatus utilising such magnets. Such magnets can cause injury to a worker's fingers and hands during assembly of an apparatus when attempting to place such magnets on a ferromagnetic support member or backing plate.
In many situations flat plate type magnets are less costly than other magnetic separators to manufacture and would have a wider usage if such could be made to be more efficient for critical uses with more catch and retain capability as well as being easier to clean off the magnetic particles retained.
Recent improvements to magnets in this technical field, has largely been with grate type magnets. Flat and plate type magnets have remained almost the same for decades substituting only newer materials such as rare earth for older materials such as ferrites and alnico alloys.
The present invention seeks to overcome at least some of the abovementioned disadvantages by providing a apparatus for entrapping magnetic material.